Protein-rich food matrices from alternative and conventional sources differentially shape gut microbiota, metabolic function, and muscle protein synthesis.

Systematic comparison of seven animal protein sources reveals more favorable glucose homeostasis in mice fed duck protein compared with pork protein, associated with gut microbiota and secondary bile acid metabolism

Animal protein sources may differentially influence glucose homeostasis, yet the underlying mechanisms remain unclear. We investigated how casein, pork, beef, mutton, chicken, duck, and goose proteins differentially affected glucose homeostasis in mice and their associations with gut microbiota and bile acids. Mice fed duck protein exhibited more favorable glucose tolerance and insulin sensitivity than those fed pork protein. These differences were accompanied by coordinated alterations in gut microbiota and bile acid profiles, including enrichment of Clostridium, increased abundance of the baiE gene, and elevated secondary bile acids. Compared with pork protein, duck protein intake increased ileal fibroblast growth factor 15 expression and portal active glucagon-like peptide-1 concentrations, upregulated adipose thermogenic and lipid oxidation genes, while downregulating hepatic gluconeogenic genes. Correlation analysis revealed associations between these genes and glucose metabolic parameters. Collectively, alterations in the microbiota–bile acid axis may contribute to the favorable glucose homeostasis observed in duck protein-fed mice.

Dietary Bacillus sp. ‌Modulates Multi-tissue Metabolism Through Gut Microbiota Remodeling in High-fat Fed Larimichthys crocea.

Integrated Assessment of the Functional Activity of the Gut Environment and Metabolic Profiles in Rats Fed an Insect-Based (Tenebrio molitor) Diet

Edible insects are increasingly proposed as sustainable protein sources in animal nutrition, yet their effects on gut microbial function, intestinal safety, and systemic metabolism require comprehensive evaluation. This study investigated the impact of a diet containing 35% Tenebrio molitor meal on the functional activity of gut environment and host metabolic profiles in rats, in comparison with diets containing chicken hydrolysate or a standard laboratory diet. Female Wistar rats were fed the experimental diets for 60 days, after which fecal short-chain fatty acids (SCFAs), microbial enzyme activity, fecal water genotoxicity, and liver and spleen metabolomes were assessed. Rats fed the T. molitor diet exhibited significantly lower fecal concentrations of major SCFAs, including acetate, butyrate, valerate, and branched-chain fatty acids (BCFAs), indicating altered colonic fermentation. Both β-glucosidase and β-glucuronidase activities differed significantly between groups and were highest in the T. molitor group. β-Glucuronidase activity also decreased over time, whereas no significant group vs. time interaction was observed. Fecal water genotoxicity decreased markedly in the T. molitor group over time. Untargeted UHPLC–HRMS metabolomics revealed pronounced diet-dependent differences in metabolite profiles. In the liver, the insect-based diet was associated with the enrichment of glycerophospholipid metabolism, primary bile acid biosynthesis, and pyrimidine metabolism pathways, as well as lower abundance of metabolites assigned to riboflavin- and phenylalanine-related pathways. In the spleen, diet-associated differences involved metabolites assigned to lipid-related pathways, including glycerophospholipid, linoleic acid, and steroid-related metabolism, as well as nucleotide-associated pathways. These findings support further evaluation of complete insect-based formulations and highlight specific metabolic pathways that should be considered when evaluating the safety and physiological implications of insect-based feeds.

Gut microbiome-metabolome interactions during varied low-carbohydrate food consumption.

Low-carbohydrate (LC) foods have been associated with weight loss, insulin resistance, and reduced inflammation. Gut microbes may drive these effects by changing the host's immune and metabolic state, yet the optimal replacement strategies (e.g., protein vs. fat) and the biochemical impacts are still uncertain. Thus, we conducted a randomized cross-over study in canines (n = 35) using a high-carbohydrate food for 4 wk, followed by two 5-wk intervals of LC foods replacing carbohydrates with fat or protein. Feces and blood samples collected after each interval underwent metabolome profiling, as well as shotgun metagenomic and metatranscriptomic sequencing from feces. We observed strong associations between food and overall fecal and serum chemical and gut microbial composition. Bifidobacterium spp. were significantly reduced during consumption of either LC food, whereas many species from Firmicutes increased. In addition to broad taxonomic changes, we also found that several microbially associated metabolites (tryptophan derivatives, secondary bile acids, and short-chain fatty acid fermentation) shifted in abundance in response to differing LC foods. Broadly, we also identified a strong trend toward decreased amino acids in the feces of dogs fed LC foods, particularly the high fat food. Coupled with decreased fecal dipeptide levels and increased fecal ammonia, these findings indicate a broad metabolic shift within the gut microbiome, potentially toward protein catabolism. Together, the data suggest that diverse carbohydrate replacement strategies induce extensive gut reprogramming, with some changes dependent on whether carbohydrate energy was replaced with fat or protein.

Comparison of the effects of four commercially available prescription diet regimens on the fecal microbiome in healthy cats.

Diet significantly influences the gut microbiota, with variations in macronutrient content (proteins, fats, and carbohydrates) and the presence of non-digestible carbohydrates, such as fiber, playing crucial roles in shaping microbial composition. This study investigated the effects of four commercial prescription diets (low-carbohydrate, weight-loss, high soluble fiber, and renal) on the fecal microbiome of five healthy domestic cats using a 4×4 Latin square design. Fecal samples were analyzed using Illumina sequencing of the bacterial 16S rRNA gene to assess bacterial community structure and diversity. Results showed that cats fed the renal diet (low protein, high carbohydrate, high fat) were associated with higher relative abundances of the phylum Actinobacteria, particularly Bifidobacterium. The low-carbohydrate diet was associated with higher relative abundances of Adlercreutzia, Collinsella, and Slackia. The high-soluble fiber diet was associated with a higher relative proportion of Streptococcaceae. In contrast, the renal diet was associated with lower relative abundances of Blautia and Erysipelotrichaceae. No significant differences were observed in alpha-diversity indices among diets, whereas beta-diversity analysis showed significant differences in microbial community composition among dietary groups. These findings suggest that dietary composition may influence the fecal microbiome in healthy cats. However, given the exploratory design and compositional nature of the sequencing data, these findings should be interpreted cautiously and considered hypothesis-generating.

Fermented Liquid Feeding Modulates Intramuscular Fat Deposition and Lipid Composition in Pork: Integrated Metabolomic and Proteomic Insights

Fermented liquid feeding (FLF) has been proposed as a nutritional intervention with the potential to influence pork quality, yet its effects on intramuscular fat deposition and muscle lipid composition remain unclear. In this study, pigs were fed a basal dry feed, liquid feed, or FLF regimen for 173 days, and porcine muscle samples were subsequently evaluated for carcass traits, meat quality, lipid composition, and molecular changes associated with lipid deposition. Compared with CON, FLF reduced average backfat thickness, while intramuscular fat and triglyceride contents in the longissimus thoracis muscle were greater than those in CON and LF (p < 0.05). Fatty-acid profiling showed that FLF increased several major fatty acids, including palmitic acid. Metabolomic analysis identified contrast-specific changes in phosphatidylserine and phosphatidylethanolamine species. Proteomic analysis, together with Western blotting and RT-qPCR, showed higher abundances of PPARγ, FASN, and downstream lipogenic transcripts in the FLF group. These findings demonstrate that FLF modulates lipid deposition and lipid composition in porcine muscle and provide mechanistic insight into the nutritional regulation of pork quality formation.